Peptides are implicated in a wide variety of biochemical processes in humans and other mammals. The design of peptide mimics which are resistant to degradation by proteolytic enzymes has become of increasing interest to peptide chemists. A primary goal has been to reduce the susceptibility of mimics to cleavage and inactivation by peptidases while maintaining certain desired biological, chemical, and/or physical properties of a targeted peptide. As a result, the design and synthesis of non-peptidal peptidomimetics has emerged as an enterprise spanning organic, bioorganic, and medicinal chemistry. Frequently, the design and/or synthetic considerations which attend development of peptide mimics are not easily resolved. For example, there is mounting evidence that hydrogen bonding involving the amide backbones of peptide hormones and their receptors is not required for receptor binding or activation, but that hydrogen bonding involving the amide backbone plays a critical role in the binding of peptidal inhibitors to proteolytic enzymes. Because non-peptidal enzyme inhibitors must mimic both the .beta.-strand conformations and, at least in part, the hydrogen bonding capabilities of their peptide counterparts, the design of such inhibitors is considerably more difficult than the design of non-peptidal hormone-receptor ligands.
There remains a need in the art for metabolically stable chemical compounds which effectively mimic the biological, chemical, and/or physical properties of naturally-occurring or synthetic peptides, particularly those having .beta.-strand conformations.